An optical transport network (OTN) includes a set of optical network elements (e.g., network devices), connected by optical fiber links, that provide transport, multiplexing, routing, management, supervision, and survivability functions for optical channels carrying optical signals. An OTN may provide transport for any digital client signal carried via any protocol that can be encapsulated in a format acceptable to the OTN. A metropolitan OTN is a geographical subset of an OTN that spans a geographical metropolitan area within an urban or suburban region, that is distinct from a core or backbone, which interconnects various metropolitan OTNs. Bandwidth requirements from end customers have increased substantially, and the resulting congestion and complexity has created a growing demand for higher bandwidth interfaces, such as interfaces provided by metropolitan OTNs. Metropolitan OTNs are inherently designed for short to medium length distances in metropolitan areas; that is, typically, within the limits of a single optical span and often less than a predetermined distance. Metropolitan OTNs are designed to provide services to a variety of customers with ranging requirements (e.g., from Digital Signal 0 (DS0) to 10 Gigabit Ethernet (10GE) services).
ITU-T G.872 defines the architecture of an OTN as including multiple layers, such as an Optical Transmission Section (OTS), an Optical Multiplex Section (OMS), and an Optical Channel (OCh). ITU-T G.709 defines the OCh layer structure and a frame format at an Optical Network Node Interface (ONNI) level. Each layer of transported information is made up of a payload and overhead. The OCh layer includes two main units (e.g., an Optical Data Unit of a particular level (k) (ODUk) and an Optical Transport Unit (OTU)), and transports payloads and associated overhead information. In particular, the purpose of the ODUk overhead is to carry information managing and monitoring an end-to-end connection crossing an OTN. The OCh layer and the ODUk layer span multiple layers, which may add to the complexity of the OTN. Furthermore, the OCh layer is an entirely optical layer, whereas the ODUk layer is not an entirely optical layer (e.g., the ODUk layer performs some electrical functions).
Fourth generation (4G) cellular networks include a radio access network (e.g., a long term evolution (LTE) network or an enhanced high rate packet data (eHRPD) network) and a wireless core network (e.g., referred to as an evolved packet core (EPC) network). The LTE network is often called an evolved universal terrestrial radio access network (E-UTRAN). The EPC network is an all-Internet protocol (IP) packet-switched core network that supports high-speed wireless and wireline broadband access technologies. An evolved packet system (EPS) is defined to include both the LTE (or eHRPD) and EPC networks.
Wireless service providers utilize circuits provided by mobile switching offices (MSOs), incumbent local exchange carriers (LECs), and other providers whose metropolitan (metro) OTNs are not optimized for LTE traffic patterns. This may result in inefficient utilization of resources, increased latencies, and increased costs. In practice, a wireless service provider's network engineering team typically constructs an overlay network to support LTE network elements. This approach force fits a new traffic pattern and new network elements onto existing OTNs that were designed for different traffic patterns. The wireless service provider incremental order circuits as capacity requirements grow, and a transport engineer monitors Layer 1 traffic and grows capacity using a localized view of individual links However, as LTE traffic increases by an order of magnitude, such incremental approaches will not scale.